Relay for synchronizing systems



May 28, 1935. g JENKINS 2,002,664-

RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 21, 1927 3Sheets-Sheet l anwntoz c. F. JENKINS 2,002,664

RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 21, 1927 May 28,1935.

3 Sheets-Sheet 2 anbentoz May 28, 1935. F, JENKINS 2,002,664

- RELAY FOR SYNCHRONIZING SYSTEMS Original Filed July 2l, 1927 3Sheets-Sheet 3 0, 5 ,va is Jan Mb;

anvzntoz 83 fitted Leaf Patented May 28, 1935 UNITED STATES RELAY FOBSYNGHBONIZING srs'rsnrs Charles Francis Jenkins, Washington, D. 0.,assignor, by mesne assignmentyto Radio Corporation of-America, acorporation of Delaware Original application July 21, 1927, Serial No.207,515, now Patent No. 1,766,644, dated June 24, 1930. Divided and thisapplication May 22, 1930, Serial No. 454,590

3 Claims. (Cl. 200-413) This invention relates to picture transmissionsystems, and in particular to arrangements for maintaining synchronousoperation between the transmitting apparatus at the transmitting sta-- 5tion and the receiving apparatus at the receiving station, and is adivision of application Serial No. 207,515,,filed July 21, 1927 whichhas matured into Patent- #1,766,644, granted June-24, 19301 An ob'ject'of myinvention is to provide means for automatically-maintaining adefinite speed relationshipbetween the transmitting and receivingapparatus.

Another object of my invention is to devise novel relay apparatuscapable of responding to electric current variations .of relatively highfrequency.

My invention is illustrated in the accompanying drawings in which likereference characters represent like parts.

Figure 1 is a diagrammatic showing of one form of my invention employedat the receiving station.

Fig. 2 is a diagrammatic representation of a second form ofapparatusemployed at the receiving station.

Fig. 3 is a third modification of the invention.

In Figure 1, a motor M is arranged to drive a cylindrical" drum C uponwhich is mounted the surface or filrnxwhich is to receive the picturebeing transmitted. The motor M comprises an armature A- and a fieldwinding F, each of which is supplied .with current from the battery B.The armature circuit of the motor is completed from battery 13 throughthe output circuit of amplifier A3, armature A, and back to battery B.The armature also has a shunt circuit from battery B through resistanceRI.

The receiving station is provided with a radio receiving set comprisinga detector DI and an amplifier Al. Connected to the output circuit ofamplifier Al is a second amplifier A2, the output circuit of whichcontains an incandescent lamp L. The picture recording apparatus is alsoconnected to the output circuit of amplifier Al and comprises, forexample, a solenoid S arranged to operate an inking pen P. A lens Ll isarranged to gather the divergent rays proceeding from lamp L and focusthemupon a light-sensitive cell LS connected in the input circuit ofamplifier A3. A disc D, provided with a series of holes arranged aroundits periphery, is mounted upon the shaft of motor A and is arranged torotate in the path of the rays of light projected upon light-sensitivecell S by the lens Ll. The width of the openings in disc D is preferablyequal to half the distance between the openings, although this ratio maybe varied considerably if desired.

The operation of Figure 1 is as follows:

It is to be understood that a radio wave is being transmitted from thetransmitting station and that the wave is modulated in accordance withthe light variations of successive elementary areas of the picture beingtransmitted and also in accordance with-the speed. of'rotation of thetransmitting apparatus. The synchronizing modulations bear. a definiterelation to the 7 speed of the transmitting apparatus and may beproduced in any desired manner, but I. prefer to employ a light-chopperfor this purpose, as disclosed in my Patent No. 1,694,065 granted December 4, 1928. The modulated wave is received at the receiving stationand detected by detector DI to derive therefrom low frequency currents.

which represent both the picture light variations and the synchronizingimpulses. This complete current is supplied to amplifier Al where it isamplified and supplied to the output circuit. The amplified current issupplied to the recording apparatus which responds to the picturevariations and causes the pen P to record upon the picture receivingsurface, mounted upon drum C, ink marks corresponding to the darkportions of the picture being transmitted. The recording apparatus neednot necessarily respond to the synchronizing interruptions orvariations. A portion of the current in the output circuit of amplifierAl is supplied to the input circuit of amplfier A2, and lamp Ll iscaused to vary in intensity inaccordance with the current variations.Accordingly, the beam of light falling upon the light-sensitive cell Swill vary in intensity in accordance with the synchronizing variations.The beam of light is also subject to control by disc D in the followingmanner: In case the motor M is rotating at such speed that the holes indisc D rotate past the beam at a frequency equal to the frequency of thesynchronizing variations, and the phase relation of the disc withrespect to the synchronizing impulses is such that each pulse reaches amaximum as a hole in disc D is centered with respect to the beam oflight, the effect of the beam of light upon the light-sensitive cell LSwill be a maximum. It will thus be seen that light-sensitive cell LSwill be intermittently illuminated at a frequency equal to that of thesynchronizing variations. The light-sensitive cell will cause amplifierA3 to produce corresponding current variations in the armaturecirmaximuni when a solid portion of disc D is passing in front of thelight ray, the eifect of the ray upon light-sensitive cell LS will be aminimum, and the current variations produced in the armature circuit ofmotor M will be very small.

' For intermediate phase relations of the holes in chronizing pulses.

disc D with respect to the synchronizing pulses. the efiect of the lightrays upon the light-sensitive cell will be to produce intermediatevalues of current variation in the armature circuit. The speed of motorM is adjusted by resistance RI to such value that it is slightly belowthe desired synchronous speed. The efiect of the current pulses producedby the light-sensitive cell 15 in the armature circuit is to increasethe motor speed. Accordingly, disc D will assume such phase relationwith respect to the synchronizing pulses or variations of lamp L thatthe amplitude of the'current pulses produced by LS is just suiiicient tomaintain the motor in synchronous operation with the incoming syn- Incase the load upon the motor is increased for any reason, disc D willlag behind the synchronizing pulses by an amount suflicient to increasethe amplitude of the current pulses produced by light-sensitive cell LSand to thereby supply to the armature A, increased current sufilcient toaccommodate the increased load. Conversely, if the load is dewill becorrespondingly reduced, and the motor will be prevented from gettingout of synchronism.

The arrangement shown in Fig. 2 is the same as that shown in Figure 1,except for the details of the motor control arrangement. In this figure,as in Figure I, both the armature and the field of the motor aresupplied with current from battery B. The armature circuit of the motoralso includes an adjustable resistance RI. In a shunt path aroundresistance Ri, a rotating commutator CM mounted upon the shaft of themotor is connected in series with contacts GT-CP of a special electricrelay. Therelay comprises a glass tube MF provid with an electrode Emounted in each end thereof. The tube is filled with an acidulatedsolution and also contains a globule of mercury GM immersed within thesolution. The insulated contacts GT-CP are mounted upon the tube andextend into the solution and normally contact with the globule ofmercury as shown in the figure. Electrodes E--E are connected to theoutput circuit of amplifier AI, and contact points GT-CP are connectedin series with commutator CM in a shunt circuit around resistance RI inthe armature circuit. r

The operation of Fig. 2 is as follows:

The speed of motor M is adjusted byresistance RI until it is slightlylower than the desired synchronous speed. With contacts GT-CP bridged bymercury GM, resistance RI will be periodically short-circuited bycommutator CM, twice for each revolution, and e time of shortcircuitwill depend upon the extent of the contact surface of the commutator andupon the speed electrodes E-E, the globule of mercury elongates andbreaks the connection between contact points GT-CP. The connectionbetween contacts GTCP will, therefore, be broken synchronously with thesynchronizing impulses. 5

It will thus be seen that the efiectiveness of resistance RI in thearmature circuit is dependent upon the conjoint action of the commute.tor CM and the relay, and the time of shortcircuit of resistance RI isdependent upon the phase relationship existing between the commutatorand the relay. If the commutator andthe relay operate simultaneously toclose their respective contacts, resistance RI will be effectively cutout of the armature circuit for a maximum period. If the commutator andrelay become displaced in phase in their operation the period ofshort-circuit will be reduced and resistance RI will have greater eflectin limiting the speed of motor -M. Accordingly, with a given load uponthe motor and with a given adjustment of the circuits, the motor M willautomatically adjust commutator CM to such phase relation with respectto the relay operation that the efi'ectiveness of resistance RI in thearmature circuit is just sufiicient to maintain the motor' atsynchronous speed. It the load upon the motor is increased for anyreason, the commutator CM tends tolag behind the operation of the relayand thereby increases the period of shortcircuit of resistance RI whichwill tend to increase the speed of the motor. Commu ator CM willautomatically assume such position that resistance RI is efiectivelyshort-circuited for a period of time suflicient to increase the armaturecurrent by an amount necessary to compensate for the increased load.Conversely, if the load upon the motor is decreased, the commutator CMtends to advance in phase relation with respect to the operation of therelay and thereby decrease the period of short-circuit of resistance R!which will ofiset the tendency of the motor to increase in speed abovesynchronous speed.

The arrangement shown in Fig.3 is the same as that shown in Fig. 2,except for the details of the relay. The relay shown in Fig. 3 comprisesa contact arm CA pivoted at a point (a). Cooperating with the contactarm is a stationary contact plate CP. The arm CA is normally held out ofcontact with plate CP by means of a wire W, one end of which is attachedto the arm and the other end is anchored to a fixed terminal.

A spring SI is attached to the arm CA and tends I, to cause the arm tocontact with plate CP. Wire W is connected to the output circuit ofamplifier AI, and contact arm CA and plate CP are connected in serieswith commutator CM in a shunt path around resistance RI. Wire W is madeof such material and such diameter that it is readily heated by currentsupplied from no amplifier At. The effect 0! the pulsating currentflowing in wire W is to cause the wire to become elongated periodicallyand in syn- .chronism with the synchronizing impulses.

the amplified current. Thus, the .relay contacts will be closedperiodically and in synchronism with the synchronizing signals. Theaction of the arrangement shown in Fig. 3 will be readily understoodfrom the foregoing explanation of the operation of Fig. 2.-

It is apparent that the arrangements shown I in Figs. 2 and 3 will alsooperate with-only the relay connected in the shunt path aroundresistance RI, and the commutator CM connected in the armature circuitso as to periodically interrupt the total armature current.

While I have shown symbolically, and for the purpose of illustrationonly, a recording apparatus comprising an inking pen P operated by amagnet S, it will readily be understood that any other well known typeof recording apparatus may be employed, such for example, as well knownphotographic recording apparatus.

The circuits of the relays have very little inductance and offer smallimpedance to high frequency currents.

It is to be noted that in Figure 1, I employ a form of electric relayhaving no moving mechanical parts, and the motor control system does notemploy vibrating or sliding electric contact device.

What is claimed is:

1. An electric relay comprising a, pair of spaced input terminals and apair of spaced contact points, said contact points being normallybridged by a body of mercury, said mercury being interposed between saidinput terminals wherebywhen current is applied thereto the mercuryelongates in a certain direction and interrupts the connection betweensaid contact points.

2. An electric'relay comprising a receptacle containing an acidulatedsolution, a pair of spaced input terminals having electrical contactwith the solution, a body of mercury immersed in said solution andlocated between the input terminalsQand a pair of spaced contacts sopositioned as to be normally bridged by said mercury but disconnectedupon flow of current between the input terminals.

3. An electric relay comprising a receptacle containing an acidulatedsolution, a body of mercury immersed in saidsolution, a pair of contactpoints, and a pair of input terminals, whereby current supplied to saidinput terminals controls the electrical connection of said con- 20 tactpoints through said body of mercury.

FRANCIS JEN'HNS.

